Measurements of whispering gallery modes (WGMs) have been used successfully to detect the binding of single biomolecules (A. M. Armani, R. P. Kulkarni, S. E. Fraser, R. C. Flagan, and K. J. Vahala, “Label-free, single molecule detection with optical microcavities,” Science 317(5839), 783-787 (2007)). WGM detection and measurement takes advantage of the resonant circulation of light around the circumference of a circular cavity to achieve such high sensitivities. However, coupling light into devices employing WGM detection and measurement is typically achieved using tapered optical fiber (F. Vollmer, D. Braun, A. Libchaber, M. Khoshsima, I. Teraoka, and S. Arnold, “Protein detection by optical shift of a resonant microcavity,” Appl. Phys. Lett. 80(21), 4057-4059 (2002)) or a prism, and therefore a complete integrated system cannot be fabricated using standard photolithography techniques. There is a need in the art for label-free ultra-sensitive biosensors that can be miniaturized and integrated on a planar substrate and that can be fabricated using standard photolithography techniques.
Citation or identification of any reference in Section 2, or in any other section of this application, shall not be considered an admission that such reference is available as prior art to the present invention.